1. Fig. 1 General characterizations of Bi2O2Se single crystals.
General characterizations of Bi2O2Se single crystals. (A) Body-center tetragonal crystal structure of Bi2O2Se, consisting of alternating Bi2O2 and Se layers. (B) (i) Optical image of a Bi2O2Se single crystal, showing the layered structure and shining cleaved surface. (ii to iv) XRD pattern of the (001), (100), and (010) surfaces, respectively. (v) Core-level photoemission spectrum, showing the characteristic peaks of Bi5d and Se3d levels. a.u., arbitrary units. (C) (i) Hall mobility (μhall) and carrier density (n) as a function of temperature in Bi2O2Se single crystal. (ii) SdH oscillatory part of the longitudinal magnetoresistance as a function of applied perpendicular magnetic field (the non-oscillatory background has been removed). (D) (i) Illustration of the cleavage process, leaving half Se atoms attached to each Bi2O2 layer (see text for more discussion). (ii) ARPES broad contour maps of conduction band (CB) minimum and valence band (VB) maximum, with the Brillouin zone (BZ) overlapped (blue frames). The indirect bandgap (~0.8 eV) is indicated.
Cheng Chen et al. Sci Adv 2018;4:eaat8355
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